Plastic container blank



Jan. 10, 1961 c. E. PALMER 2,967,654

PLASTIC CONTAINER BLANK Filed Dec. 29, 1958 l'9 ze m /Z 24 A29 2 /3 26 IN V EN TOR.

CHARLES E. PALMER United States Patent O PLASTIC CONTAINER BLANK Charles E. Palmer, Turnpike Road, Somers, Conn.

Filed Dec. 29, 1958, Ser. No. 783,308

2 Claims. (Cl. 229-35) The present invention relates to plastic containers and is concerned more particularly with containers, such as trays or the like formed of stiff plastic sheet material, such as polystyrene. The invention also includes the novel blank used in forming the container and the method of forming the blank into a self-sustaining container.

Containers formed of plastic sheet material generally are formed in accordance with the techniques employed in forming paper or paperboard containers from blanks of suitable sheet material which usually includes scoring the blank along the fold lines and the step of gluing the overlying flaps or parts in assembled position. Such techniques are generally unsatisfactory when used with plastic sheet material since the resulting product is generally inferior in rigidity and strength and is generally unsightly in appearance, particularly where a clear and substantially transparent plastic sheet material is used. Furthermore, such techniques do not take advantage of the unique properties of plastic sheet material as compared to paperboard and the like which may be used to facilitate formation of the container.

An object of the present invention is to provide a blank and method for forming containers of plastic sheet material which can be used with automatic packaging machinery to form containers of plastic sheet material in an inexpensive and price competitive manner.

A further object is to provide such a blank and method which will provide a plastic container of superior strength and rigidity and one which will retain its form under normal conditions of use.

A further object is to provide a plastic container having an improved structural form which is attractive and appealing in appearance, such that it may be used to package a variety of goods and commodities.

I Other objects will be in part obvious and in part pointed out more in detail hereinafter;

The invention accordingly consists in the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

In the drawings:

Fig. 1 is a plan view of a preferred blank of plastic sheet material formed in accordance with the invention;

Fig. 2 is a perspective view of the blank showing the side walls and locking flaps folded into upright position;

Fig. 3 is an enlarged fragmentary perspective view of the folded blank of Fig. 2 during the initial stages of folding the end wall and attaching the locking flap thereof to the side wall;

Fig. 4 is a further enlarged fragmentary perspective view of the blank during a subsequent stage of the formation of the container;

Fig. 5 is a partial plan view of the blank in the container forming stage shown in Fig. 4; and

Fig. 6 is a fragmentary perspective view of the completed container.

Referring to the drawings, the exemplary blank formed 2,967,654 Patented Jan. 10, 1961 in accordance with the invention is indicated generally as 10 and in the specific embodiment illustrated in the drawings, this blank is generally rectangular in shape and comprises a bottom panel 11 having side walls 12 and 13 integrally joined thereto along unscored lines 14 and 15,

' respectively, and the end walls 16 and 17 integral-1y joined thereto along unscored lines 18 and 19, respectively. The blank 10 is formed of relatively rigid plastic sheet material, such as biaxially oriented polystyrene. The term polystyrene-like plastic sheet material refers to plastic sheet which is rigid in the sense that it will resist folding or creasing and is dimensionally stable. These materials in thin section, such as sheets of less than 20 mils thickness, however, can be readily flexed without permanent deformation. Generally the sheet used for the present invention will be 5 to 17 mils in thickness.

To form a container from the blank 10, the side walls 12 and 13 are first bent or folded into an upright position to form the corners for edges 14 and 15. The blank may be folded in accordance with the technique disclosed and claimed in my copending application Serial No. 741,328, filed June 11, 1958, wherein the blank is folded through an angle of approximately and then springs back to assume a permanent set at the desired right angle. The blank is not scored at the fold lines but the surface is smooth and unbroken. integrally formed at each side edge of each end wall is a locking flap 20 which will be described in more detail hereinafter. Simultaneously with the bending of the side walls 12 and 13, it is preferred to also bend the locking flaps 20 into an upright position as shown in Fig. 2.

Each of the locking flaps 20 is formed with an integral tab 21 having a rearwardly inclined arcuate leading edge 22 and is so configured as to provide a transverse nose portion 23 adjacent but spaced from the edge 24 by the notch 25. The flap 20 and integral tab 21 are arranged for cooperation with a retainer flap 26 formed in the ad jacent end portion of each of the side walls 12 and 13. In the preferred embodiment, the retainer flap 26 is formed by means of a non-linear and generally triangular cut pointing towards the adjacent end of the side panel and beginning at the lowermost point 27 and serving to form a generally longitudinally extending shoulder 28 in the side wall. The extremities of the cut are reversely curved as shown to eliminate linear stress and overcome the tendency of the material to tear when the flap 26 is flexed relative to the side wall.

The blank provided in accordance with the present invention is unscored, so that the surfaces of the blank at the interconnections between the bottom panel and the side and end wall panels, and between the end wall panels and the locking flaps are smooth and unbroken.

During the assembly of the container, as the end wall is being folded to an upright position, the locking flap 20 is first introduced behind the retainer flap 26 as illustrated in Fig. 3 of the drawings. The nose portion 23 of the tab 21 extends above the shoulder 28 and, accordingly, cannot pass to the interior surface of the side wall by movement parallel to the general plane of the side wall, particularly since the end wall, when it reaches an upright position, engages along its rearwardly inclined arcuate leading edge 22 with the lowermost point 27 of the tn'angular slit and this normally prevents further movement of the end wall beyond the upright position. Accordingly, in order to assemble the container, during further folding pressure on the end wall the tab portion 21 of the locking flap 20 is bent inwardly of the container as indicated in Figs. 4 and 5 of the drawings and at the same time, the extreme end portion of the side wall 12 is distorted or flexed inwardly along the interior surface of the end wall 16, the tab and side wall turning or flexing about the point of abutment of the tab and slit. This permits the tab 21 to enter the slit formingthe retainer flap 26 and to extend beyond the interior surface of the side wall 13. The guiding of the locking flap 20 in this manner can easily be accomplished in automatic folding machinery of the type which has been developed for folding plastic sheet material, such as polystyrene. In the preferred embodiment, the edges 29 of the side walls 12 and 13 are tapered to facilitate this flexing movement and to permit the overfolding necessary to achieve a vertical set upon relaxation in accordance with my hereinbefore identified application.

' Upon release of the blank after it has been placed in the position shown in Figs. 4 and 5 of the drawings, the inherent resiliency or spring-back of the plastic sheet material will cause the end wall and side walls to return to the rectilinear position shown in Fig. 6 of the drawings with the tab 21 and flap 26 securely interlocked and rigidly interconnected. A characteristic of plastic sheet material, such as polystyrene, is that although the end walls have to be folded more than 90 in order to interlock the end and side walls, this folding through an angle greater than 90 is also necessary to allow for springback of the material in order to cause the walls to take a permanent set at the desired 90 angle. As will be apparent from a consideration of Fig. 6 of the drawings, the completed container will be provided with a rigid corner, inasmuch as in this position the arcuate edge 22 engages the lowermost point 27 of the slit forming the retainer flap 26 and the tab portion 21 engages the shoulder 28, thus preventing movement of the end wall in either direction from the upright position.

As will be apparent from the above description, the container formed from the blank of the present invention may be made in an easy and convenient manner at low cost without the use of adhesives and provides a struc ture of pleasing appearance, taking full advantage of the inherent properties of the plastic sheet material from which the container is made.

The preferred embodiment which has been described above has been given by way of illustration and will be subject to modification within the skill of the art without departing from the scope of the invention, and all such modifications are intended to be included.

I claim:

1. An unscored container blank formed of polystryenelike plastic sheet material and including a bottom panel and integrally formed end and side wall panels adapted to be cold-folded into a rectilinear configuration, said side wall panels having tapered ends and being provided adjacent each end with a non-linear slit pointing towards the adjacent end of the side panel, each of said slits having a reversely curved inner end portion and forming an opening in the side wall panels bounded by a shoulder extending longitudinally of the side wall panel, and said end panels being provided with foldable end flaps, each flap having a tab providing a transverse nose portion and a rearwardly inclined leading edge, the leading edge of the tab being adapted to abut the inner end of the slit when the end panel is substantially vertical and the ends of the side panels and tab being adapted to flex inwardly about said point of abutment during further folding of the end panel for passage of the nose portion through said slit to engage behind the shoulder of the side wall, the surfaces of the blank at the interconnections between the bottom panel and the end and side panels and between the end panels and the end flaps being smooth and unbroken and free from weakened or scored lines.

2. An unscored container blank formed of biaxially oriented polystyrene sheet material of 5 to 17 mils thickness and including a bottom panel and integrally formed end and side wall panels adapted to be cold-folded into a rectilinear configuration, said side wall panels having tapered ends and being provided adjacent each end with a generally triangular 'slit pointing towards the adjacent end, said slit having reversely curved ends and forming an opening in the side wall panel bounded by a shoulder extending generally longitudinally of the side wall panel, and said end panels being provided with foldable end flaps, each flap having a tab with a rearwardly inclined arcuate leading edge and providing a transverse nose portion, the arcuate edge of the tab being adapted to abut the bottom of the slit when the end panel is substantially vertical and the ends of the side panels and the tab being adapted to flex inwardly about said point of abutment during further folding of the end panel for passage of the nose portion through said slit to engage behind the shoulder of the side wall, the surfaces of the at the interconnections between the bottom panel and the end and side panels and between the end panels and the end flaps being smooth and unbroken and free from weakened or scored lines.

References Cited in the file of this patent UNITED STATES PATENTS 483,502 Schmidt Sept. 27, 1892 610,950 Smith Sept. 20, 1898 691,458 Ferres Jan. 21, 1902 1,319,263 Baker Oct. 21, 1919 2,141,752 Hoarle Dec. 7, 1938 2,475,279 Dunning July 5, 1949 2,536,384 Meller Jan. 2, 1951 2,580,181 Meller Dec. 25, 1951 2,659,934 Burgess Nov. 24, 1953 FOREIGN PATENTS 24.529 Finland r- .1.

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